1. Field of the Invention
The present invention relates mainly to a real image type finder for use in cameras.
2. Description of Related Art
Among cameras having a finder optical system provided on the camera body separately from an imaging optical system, a finder such as the Galilean finder has found widespread popularity in various fields of application hereinbefore. However, with the improved imaging systems being put on the market, the market preference trend has been switched to real image type finders which can form an image of an object with a relatively high magnification power and a bright frame of the view field. Additionally, with the market trend moving toward more compact cameras, a need has arisen for an image type finder which may form an image with high magnification power and a reduced overall length.
However, the prior art camera finder suffered from the disadvantage that the finder frequently caused a flare around an eye point with the increase of the magnification power in each of the lenses which constitute the optical system; this resulted in the image being quickly impaired by the presence of such flares etc., when a viewer's pupil moved while looking in through the finder.
Recently, a zoom lens with a highly variable magnification power has become a popular item for use in the imaging system, and it has also generated demand for real image finder with a highly variable magnification power ratio and high magnification power.
However, in a prior art zoom finder, the eye point diameter is subject to substantial variation due to its variable power. That is, the eye point diameter is subject to excessive increase at the end of the wide-angle position, and thereby causes a substantial flare to be created around the eye point.
There was also a problem with the eye point diameter being reduced excessively at the end of the telephoto position; this kept the viewer from seeing the object, when the user manipulate the camera to reduce the eye point diameter at the end of the wide-angle position in order to solve the problem.
When the aperture is apart from the object optical system, quality of image-forming in the object optical system deteriorates, and diameter of the front lens of the object optical system has to be increased, since light at the periphery of the field-of-view passes through the periphery of the object optical system.